On each firing, look for instances of the pattern specified by pattern
in stringToEdit and replace them with the string given by
replacement. If replaceAll is true, then replace
all instances that match pattern. Otherwise, replace only
the first instance that matches. If there is no match, then the
output is the string provided by stringToEdit, unchanged.
The pattern is given by a regular expression.
For a reference on regular expression syntax see:
http://download.oracle.com/javase/tutorial/essential/regex/.

The replacement string, as usual with string-valued parameters
in Ptolemy II, can include references to parameter values in scope.
E.g., if the enclosing composite actor has a parameter named "x"
with value 1, say, then the replacement string a${x}b will become
"a1b".

In addition, the replacement string can reference the pattern
that is matched using the syntax "$$0". For example, the regular
expression "t[a-z]+" in pattern will match the character t followed by a
sequence of one or more lower-case letters.
If replacement is "p$$0" then "this is a test" becomes
"pthis is a ptest".

If the pattern contains parenthesized subpatterns, such
as "(t[a-z]+)|(T([a-z]+))", then the value of replacement
can reference the match of each parenthesized subpattern with
the syntax "$$n", where "n" is an integer between 1 and 9.
For example, if pattern="(t[a-z]+)|(T([a-z]+))"
and replacement="p$$1$$3", then "this is a Test" becomes
"pthis is a pest". The index "n" corresponds to the order
of opening parentheses in the pattern.

To get a "$" into the replacement string, use
"\$$". To get a "\" into the replacement string, use "\\".